Harriet bought 4 boxes that each have 30 bags of chips. she already had 80 bags of chips. if she then sells 200 bags of chips, how many bags of chips does she have left?

(n^3 - n)

= n(n-1)(n+1)

since it is divisible by 3 and 2 ,because it is a multiple 3 consecutive number

if, n-1 is odd then n+1 is also odd, then it is a multiple of 9

but if, n-1 is even then n+1 is also even, then it is a multiple of 4

so, largest multiple = max(9*2, 4*3) = max(18, 12) = 18

17.08

correct me if i am wrong.